A saddle-type vehicle such as a motorcycle or a buggy is generally provided with a power unit integrally including an engine (internal combustion engine) and a transmission device. Gear shifting is achieved by operating a change pedal provided on the side portion of the transmission device with an operator's foot. A shift spindle, which is operated to rotate by the change pedal, is formed with a groove with which a positioning pin mounted to a cover of the power unit engages for constraining displacement of the shift spindle in the direction other than the direction of rotation thereof (for example, see JP-A-2001-108093).
When assembling the shift spindle to the power unit, the positioning pin is inserted into a through hole on the cover from the outside of the power unit to be brought into engagement with the groove of the shift spindle positioned inside the power unit. This work, however, is difficult because the interior of the power unit cannot be viewed easily.